// Start with a small aspiration window and, in the case of a fail
// high/low, re-search with a bigger window until we don't fail
// high/low anymore.
- int failedHighCnt = 0;
+ failedHighCnt = 0;
while (true)
{
Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter);
constexpr bool PvNode = NT == PV;
const bool rootNode = PvNode && ss->ply == 0;
+ const Depth maxNextDepth = rootNode ? depth : depth + 1;
// Check if we have an upcoming move which draws by repetition, or
// if the opponent had an alternative move earlier to this position.
if (ttCapture)
r++;
+ // Increase reduction at root if failing high
+ r += rootNode ? thisThread->failedHighCnt * thisThread->failedHighCnt * moveCount / 512 : 0;
+
// Increase reduction for cut nodes (~10 Elo)
if (cutNode)
r += 2;
(ss+1)->pv = pv;
(ss+1)->pv[0] = MOVE_NONE;
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, false);
+ value = -search<PV>(pos, ss+1, -beta, -alpha,
+ std::min(maxNextDepth, newDepth), false);
}
// Step 18. Undo move
// CounterMove based pruning
if ( !captureOrPromotion
- && moveCount
+ && bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold
&& (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold)
continue;
// All legal moves have been searched. A special case: if we're in check
// and no legal moves were found, it is checkmate.
if (ss->inCheck && bestValue == -VALUE_INFINITE)
+ {
+ assert(!MoveList<LEGAL>(pos).size());
+
return mated_in(ss->ply); // Plies to mate from the root
+ }
tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit,
bestValue >= beta ? BOUND_LOWER :